This invention relates to a fluid power, servo-steering mechanism of the type having a common housing for the steering control valve, the servomotor and steering gear.
Auxiliary fluid power steering devices of the foregoing type are known from the German Patent Specification 19 24 032. In such devices the rotary valve body of the control valve has a large external portion thereof enclosed by fluid chambers under return pressure. A portion of one of the faces of the valve body from which the steering worm extends is exposed to one of the pressure chambers of the servomotor. Since the pressure on such face of the control valve is not compensated for, a high axial thrust corresponding to the high operating pressure in the servomotor is exerted on the control valve to correspondingly load axial bearings that must be designed to cope with such thrust. The axial thrust occurs however only when the pressure chamber of the servomotor adjacent to the control valve is acted upon by fluid under operating pressure in one direction of steering so that repetitive stress loading of the control valve results. Although axial thrust is somewhat reduced by sealing and stress relieving means associated with prior art auxiliary steering gear, the problem is not completely solved.
It is therefore an important object of the present invention to improve auxiliary steering gear of the foregoing type in such a way that the control valve is completely relieved of axial pressure forces without additional cost.